Originally Posted by Paul
Kurt,
I think 21 mpg is a little low. The 75 FI model used a "Special" thermostat. If you are using the standard looking thermostat, then the water never heats up to the proper temp and the car will run a bit on the rich side. The injector pulse width is tied to the water temp by a negative coefficient temperature sensor. So the water needs to be at 195 for the car to fully lean out at normal operating temperature.
Also, I'd bump the timing up a couple of degrees, try 5 degres advanced. Also, I'd change out the rear end grease with a synthetic, like Red Line. I'd also run a full synthetic motor oil. I'f you don't want to go that route, I would run 1 QT of Moble 1 with what ever regular oil you use. Maybe the best way to improve milage would be to throw out the points and get a Pertornix.
With these few things you should be able to eak out a couple more MPG's
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Excellent advice. So good in fact, that I had already done all of those things! The Pertronix really helped the power curve at higher RPM where the old points showed their limitations the most. And it is running at the proper temperature with the correct thermostat.
I suspect Bob is on the mark regarding the injectors; they are the originals and they're probably worn and crudded up as well. After I check all the basics like fuel pressure, etc., I may round up some new or reconditioned injectors from OGTS. Or if anybody has some NOS laying around, let me know?
I also have a 1.5 head with 1.9 valves, unshrouded, that I'm planning to install this summer. Should get a small bump in horsepower and mileage with that. I know it won't work miracles, maybe 2-3 mpg, and ~8 hp?
-Kurt